no arrow to go to next image

Hello,

Last week the image galleries were working properly. I would click on thumbnail and the image would have an arrow at the bottom to go to the next image. Now when I click on a thumbnail – the image pops up by itself and you have to hit the back button to go back to the main page to see the other thumbnails. Please help me fix this so it scrolls to the next image with that arrow that used to be there.
https://www.fruktradgiving.no/funnyfrog/wordpress/

Thank you in advance for your help!